Rotary position measuring instrument

Abstract

A rotary position measuring instrument that includes a light source and a graduated disk having a measuring standard. The rotary position measuring instrument including an optoelectronic detector assembly, wherein the graduated disk is rotatable relative to the light source and the detector assembly about an axis of rotation, wherein rotary-angle-dependent position signals are detectable via the detector assembly. The light source is spaced apart from the measuring standard by a first distance, and the detector assembly is disposed at a second distance from the measuring standard, wherein the second distance is different than the first distance. The graduated disk includes an optical element, which has an optical effect that results in a projecting an image of the light source into a position which has a third distance from the measuring standard, wherein the third distance is different than the first distance.

Description

RELATED APPLICATIONS[0001]Applicant claims, under 35 U.S.C. §119, the benefit of priority of the filing date of Sep. 13, 2011 of a German patent application, copy attached, Serial Number 10 2011 082 570.3, filed on the aforementioned date, the entire contents of which is incorporated herein by reference.BACKGROUND[0002]1. Technical Field[0003]The present invention relates to a rotary position measuring instrument.[0004]2. Background Information[0005]FIG. 1 shows a schematic fragmentary view of a known optical position measuring instrument that is based on a central-projection scanning principle. A light source 1 divergently illuminates a reflective measuring standard 2. The measuring standard can be embodied as either a linear or a rotary graduation, depending on whether the position measuring instrument is to be used for detecting rotary or linear relative motions. From the measuring standard 2, incident beams are reflected back in the direction of the light source 1. In a detectio...

AI Technical Summary

Benefits of technology

The present invention aims to make rotary position measuring instruments less sensitive to non-ideal distances between components and soiling of the measuring standard. The invention includes a graduated disk and an optoelectronic detector assembly. The light source is spaced apart from the measuring standard on the axis of rotation by a first distance, and the detector assembly is disposed at a different second distance from the measuring standard. The graduated disk also includes an optical element that results in a projecting image of the light source into a position that has a different distance from the measuring standard. The technical effect of the invention is to improve the accuracy and reliability of rotary position measuring instruments.

Problems solved by technology

That is, often a situation like that shown in FIG. 1 results in which the magnitude of the first distance u is different from the magnitude of the second distance v. In the example of FIG. 1, wherein u<v, fluctuations in the scanning distance cause changes in the size of the fringe pattern and, thus, cause errors in the position determination.

Further problems in such position measuring instruments result from their sensitivity to soiling on the measuring standard.

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